<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>

    #d1{
      width: 50px; height: 200px;
      background-color: red;
      position: absolute;
      /*控制元素的显示层级,值越大显示越靠前*/
      z-index: 1;
    }
    #d2{
      width: 200px; height: 50px;
      background-color: blue;
      position: absolute;
      z-index: 2;
    }
    #d3{
        width: 200px;
        height: 200px;
        /*设置超过部分是否显示 hidden隐藏  scroll 滚动显示*/
        overflow: scroll;
    }
  </style>
</head>
<body>

<div id="d1"></div>
<div id="d2"></div>
<div id="d3">
    <img src="../b.jpg" alt="">
</div>
</body>
</html>